U.S. patent number 6,321,161 [Application Number 09/392,876] was granted by the patent office on 2001-11-20 for method and system for providing guidance about alternative routes with a navigation system.
This patent grant is currently assigned to Navigation Technologies Corporation. Invention is credited to Paul Bouzide, James Herbst, Sue McGrath.
United States Patent |
6,321,161 |
Herbst , et al. |
November 20, 2001 |
Method and system for providing guidance about alternative routes
with a navigation system
Abstract
A feature for a navigation system provides an evaluation of
alternative routes. According to this feature, the navigation
system provides information to the vehicle driver about departing
from a route being followed. This allows the driver to make an
assessment whether to depart from the route being followed or stay
on the route. This feature enables driver-observable traffic
conditions to be taken into account by the vehicle driver.
Inventors: |
Herbst; James (Chicago, IL),
McGrath; Sue (Arlington Heights, IL), Bouzide; Paul
(Chicago, IL) |
Assignee: |
Navigation Technologies
Corporation (Chicago, IL)
|
Family
ID: |
23552378 |
Appl.
No.: |
09/392,876 |
Filed: |
September 9, 1999 |
Current U.S.
Class: |
701/411; 340/905;
340/995.19; 701/117 |
Current CPC
Class: |
G01C
21/3415 (20130101); G08G 1/096827 (20130101); G08G
1/096844 (20130101); G08G 1/096861 (20130101); G08G
1/096872 (20130101) |
Current International
Class: |
G08G
1/0968 (20060101); G06F 019/00 () |
Field of
Search: |
;701/210,200,201,207,209,213,117 ;340/995,905 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Cuchlinski, Jr.; William A.
Assistant Examiner: Donnelly; Arthur D.
Attorney, Agent or Firm: Kozak; Frank J. Kaplan; Lawrence
M.
Claims
We claim:
1. A method of operation for a navigation system installed in a
vehicle, the method comprising the steps of:
while the vehicle is being driven to a destination, continuously
determining a current position of the vehicle; and
when the vehicle approaches locations at which alternative roads
can be taken, advising a driver of the vehicle which of said
alternative roads to avoid.
2. The method of claim 1 wherein said step of advising the driver
which of said alternative roads to avoid is performed at each
intersection from which alternative roads can be taken.
3. The method of claim 1 wherein said step of advising the driver
which of said alternative roads to avoid is performed at major
intersections from which alternative roads can be taken.
4. The method of claim 1 wherein said step of advising is in
response to a query input by the driver to the navigation
system.
5. The method of claim 1 further comprising the step of:
prior to the step of advising, accepting an input from the driver
indicating said destination.
6. The method of claim 1 further comprising the step of:
prior to the step of advising, determining a relative cost to
follow a route to the destination along each of said alternative
roads; and
wherein said advising is based upon the relative cost of one of
said alternative roads being substantially higher than the
others.
7. The method of claim 1 wherein the step of advising is performed
only at intersections with stoplights.
8. The method of claim 1 wherein the step of advising is performed
only at intersections that meet a criterion specified by the
driver.
9. The method of claim 1 wherein the step of advising is performed
only at intersections of a specified rank.
10. The method of claim 1 further comprising the step of:
prior to the step of advising the driver, accepting a configuration
parameter from the driver indicating a type of intersection for
which advice is to be provided.
11. A method of operation for a navigation system installed in a
vehicle, the method comprising the steps of:
determining a first solution route to a destination specified by a
driver of the vehicle;
providing driving instructions to the driver of the vehicle to
drive along the first solution route to the destination;
while the driver is driving along the first solution route,
continuously determining a current position of the vehicle;
while the driver is driving along the first solution route,
providing an evaluation to the driver about whether a departure
from the first solution route at a first location should be
avoided.
12. The method of claim 11 wherein the evaluation comprises:
an indication of an expected time of arrival at the destination via
the first solution and an expected time of arrival at the
destination via an alternative solution route that departs from the
first solution route at the first location.
13. The method of claim 11 wherein the evaluation comprises:
an indication of how much longer an alternative solution route that
departs from the first solution route at the first location would
be expected to take compared to the first solution route.
14. The method of claim 11 wherein the evaluation comprises:
an indication that an expected of time of arrival at the
destination via an alternative solution route that departs from the
first solution route at the first location is not significantly
greater an expected time of arrival at the destination via the
first solution route.
15. The method of claim 14 wherein the indication is based upon a
comparison to a predetermined threshold of a difference between the
expected amount of time to arrive at the destination via the
alternative route and the expected amount of time to arrive at the
destination via the first solution route.
16. The method of claim 15 wherein the predetermined threshold is
configurable by the driver.
17. The method of claim 11 wherein the first location is a major
intersection immediately ahead of the current position of the
vehicle.
18. The method of claim 11 wherein the first location is an
intersection specified by the driver.
19. The method of claim 11 further comprising the steps of:
determining at least one alternative route to the destination,
wherein said at least one alternative route departs from the first
solution route at the first location; and
comparing said at least one alternative route to the first solution
route to provide said evaluation.
20. The method of claim 19 wherein said at least one alternative
route avoids substantially all of the first solution route.
21. The method of claim 11 wherein said departure begins with a
U-turn.
22. The method of claim 11 wherein said first location is
observable by the driver from the current position of the
vehicle.
23. The method of claim 11 wherein the evaluation is provided in
response to a query from the driver.
24. The method of claim 23 further comprising the step of:
prior to receiving the query from the driver, identifying to the
driver at least two upcoming intersections along the first solution
route from which to select a point of departure from the first
solution route; and
accepting a selection by the driver of one of said intersections as
the first location.
25. The method of claim 23 further comprising the steps of:
prior to receiving the query from the driver, determining at least
one alternative route to the destination, wherein said at least one
alternative route departs from the first solution route at the
first location; and
comparing said at least one alternative route to the first solution
route to provide said evaluation.
26. The method of claim 11 wherein said evaluation is provided
automatically as the first location is being approached.
27. The method of claim 26 wherein said evaluation is provided
automatically only at intersections with stoplights.
28. The method of claim 26 wherein said evaluation is provided
automatically only at intersections that meet a criterion specified
by the driver.
29. The method of claim 26 wherein said evaluation is provided
automatically only at intersections of a specified rank.
30. A method of operation for a navigation system installed in a
vehicle, the method comprising the steps of:
while the vehicle is being driven to a destination, continuously
determining a current position of the vehicle; and
providing the driver of the vehicle with an evaluation whether any
alternative routes from an intersection being approached should be
avoided.
31. The method of claim 30 wherein said evaluation is provided in
response to a query from the driver.
32. The method of claim 30 wherein said evaluation is provided
automatically.
33. The method of claim 32 wherein said evaluation is provided
automatically only at intersections with stoplights.
34. The method of claim 32 wherein said evaluation is provided
automatically only at intersections that meet a criterion specified
by the driver.
35. The method of claim 32 wherein said evaluation is provided
automatically only at intersections of a specified rank.
Description
BACKGROUND OF THE INVENTION
The present invention relates to in-vehicle navigation systems and
more particularly the present invention relates to using a
navigation system interactively to provide guidance about
alternative routes while driving.
In-vehicle navigation systems are available that provide end users
(such as drivers of the vehicles in which the in-vehicle navigation
systems are installed) with various navigating functions and
features. For example, some in-vehicle navigation systems are able
to determine an optimum route to travel by roads between locations
in a geographic region. Using input from the end user, and
optionally from equipment that can determine one's physical
location (such as a GPS system), a navigation system can examine
various routes between two locations to determine an optimum route
to travel from a starting location to a destination location in a
geographic region. The navigation system may then provide the end
user with information about the optimum route in the form of
instructions that identify the driving maneuvers required to be
taken by the end user to travel from the starting location to the
destination location. The instructions may take the form of visual
and/or audio instructions that are provided along the way as the
end user is traveling the route. Some navigation systems are able
to show detailed maps on computer displays outlining routes to
destinations, the types of maneuvers to be taken at various
locations along the routes, locations of certain types of features,
and so on.
In order to provide these and other navigating functions,
navigation systems use geographic data The geographic data may be
in the form of one or more databases that include data that
represent physical features in a geographic region. The geographic
database may include data representing the roads and intersections
in a geographic region and also may include information relating to
the represented roads and intersections in the geographic region,
such as turn restrictions at intersections, speed limits along the
roads, street names of the various roads, address ranges along the
roads, and so on.
Although navigation systems provide many important features, there
continues to be room for improvements. One area in which there is
room for improvement relates to using a navigation system to
provide route guidance that takes into account driving or traffic
conditions observed by the vehicle driver. For example, the driver
may observe a traffic condition that may have an affect on how
quickly a destination is reached. According to one example, the
driver may observe that the road ahead along the calculated route
is backed up with traffic congestion. According to another example,
the driver may observe that a left turn signal in a stop light at
an upcoming intersection would allow a left turn to be made sooner
than proceeding straight ahead along a calculated route. Under
these circumstances, the driver may not be satisfied with staying
on the calculated route because conditions that the driver observes
may suggest that an alternative route may be faster. However, prior
navigation systems have not provided a way to take
driver-observable conditions into account.
It is noted that some in-vehicle navigation systems have been
proposed that obtain and use real-time traffic information.
According to one type of proposed system, data about traffic
congestion in a geographic area are collected by a traffic
information service. The collected traffic data are filtered and
processed. Then, the traffic information service broadcasts
messages that contain information about the traffic congestion
along roads in the geographic area. The in-navigation systems in
the vehicles traveling in the geographic area include equipment
that receive the messages. Programming in the in-vehicle navigation
systems use the information about traffic congestion when
calculating optimal routes and when providing route guidance.
Although these types of proposed systems can be beneficial to
vehicle users, these types of systems rely on the collection and
broadcasting of traffic congestion information by a traffic
information service. Many geographic regions may not have a traffic
information service that collects traffic data and broadcasts
messages that can be used by in-vehicle navigation systems.
Further, even if a traffic information service is available in a
geographic area, the traffic information service may collect and
broadcast traffic congestion data about only certain roads (e.g.,
those that have the highest volume of traffic). If the driver of
the vehicle with the in-vehicle navigation system is traveling on a
road that is not covered by the traffic information service, he/she
may not be able to obtain up-to-date traffic information.
Accordingly, there continues to be a need to provide alternative
ways to provide navigation assistance to a vehicle driver using a
navigation system.
SUMMARY OF THE INVENTION
To address these and other objectives, the present invention
comprises a feature for a navigation system that provides an
evaluation of alternative routes. According to this feature, the
navigation system provides information to the vehicle driver about
departing from a route being followed. This allows the driver to
make an assessment whether to depart from the route being followed
or stay on the route. This feature enables driver-observable
traffic conditions to be taken into account by the vehicle
driver.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing components of an exemplary
navigation system used in conjunction with a first embodiment.
FIG. 2 is an illustration of a vehicle dashboard in which the
navigation system of FIG. 1 is installed.
FIG. 3 is a block diagram showing portions of the navigation
application programming in FIG. 1.
FIG. 4 is a block diagram showing some of the components of the
output of the route calculation application of FIG. 3.
FIG. 5 is a map used to describe operation of an embodiment of the
detour evaluation feature shown in FIG. 3.
FIG. 6 is a flow chart showing steps performed by the embodiment of
the detour evaluation feature shown in FIG. 3.
FIG. 7 is an illustration of the display screen of the navigation
system of FIG. 2 during operation of the embodiment of the detour
evaluation feature of FIG. 3.
FIG. 8 is an illustration of the display screen of the navigation
system of FIG. 2 during operation of an alternative embodiment of
the detour evaluation feature of FIG. 3.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
I. OVERVIEW OF NAVIGATION SYSTEM
Referring to FIG. 1, there is a diagram illustrating an exemplary
configuration of a navigation system 10. The navigation system 10
is a combination of hardware and software components. In one
embodiment, the navigation system 10 is located in an automobile
12. The navigation system 10 includes appropriate positioning
system hardware 14 which in an exemplary embodiment may include a
GPS system 16 and other sensor equipment 20 that senses the vehicle
speed, heading, acceleration, etc. In addition, the navigation
system 10 includes an appropriate computer 24, including a CPU 26
and memory 28 as well as other appropriate hardware.
Also included as part of the navigation system 10 is a user
interface 31 coupled to the computer 24. The user interface 31
includes appropriate means for receiving instructions and input
from a user as well as means for providing information back to the
user. FIG. 2 shows parts of the user interface 31. In FIG. 2, the
navigation system 10 is shown installed in a dashboard 33 of the
vehicle 12. The user interface 31 is installed on a front panel of
the navigation system 10 so that it is accessible to the driver
and/or passengers. The user interface 31 includes an input keypad
36 and possibly other input hardware and software, such as a
microphone, voice recognition software, and so on, through which
the driver (or passenger) can request navigation information and
services. The user interface 31 may also include output hardware
and software, such as a display screen 42, speakers 43 (shown in
FIG. 1), speech synthesis software, etc., through which the driver
or passengers can be provided with information from the navigation
system 10. The user interface 31 may also include a remote control
unit 48 mounted in a bracket located on a front panel of the
navigation system 10. The remote control unit 48 may include its
own input keys and possibly a display screen.
Referring again to FIG. 1, all of the components described above
may be conventional (or other than conventional) and the
manufacture and use of these components are known to those of skill
in the art. For example, the processor 26 may be of any type used
in navigation systems, such as 32-bit processors using a flat
address space, such as a Hitachi SH1, an Intel 80386, an Intel 960,
a Motorola 68020 (or other processors having similar or greater
addressing space). Processor types other than these, as well as
processors that may be developed in the future, are also
suitable.
In order to provide navigation features to an end user, the
navigation system 10 uses geographic data 50. The geographic data
50 includes information about one or more geographic regions or
coverage areas. The geographic data 50 may be stored in the vehicle
12 or alternatively, the geographic data 50 may be stored remotely
and made available to the navigation system 10 in the vehicle 12
through a wireless communication system which may be part of the
navigation system 10. In another alternative, a portion of the
geographic data 50 may be stored in the vehicle 12 and a portion of
the geographic data 50 may be stored in a remote location and made
available to the navigation system 10 in the vehicle 12 over a
wireless communication system from the remote location.
In the embodiment shown in FIG. 1, some or all of the geographic
data 50 are stored on a medium 52 which is located in the vehicle
12. Accordingly, the navigation system 10 includes a drive 54 (or
other suitable peripheral device) into which the medium 52 can be
installed and accessed. In one embodiment, the storage medium 52 is
a CD-ROM disk. In another alternative embodiment, the storage
medium 52 may be a PCMCIA card in which case the drive 54 would be
substituted with a PCMCIA slot. Various other storage media may be
used, including fixed or hard disks, DVD disks or other currently
available storage media, as well as storage media that may be
developed in the future.
The geographic data 50 may be stored in the form of one or more
computer-readable data files or databases. The geographic data 50
may include information about the positions of roads and
intersections in or related to a specific geographic region or
area, and may also include information about one-way streets, turn
restrictions, street addresses, cost of travel factors (i.e.,
relative times associated with travel along various road segments),
alternative routes, hotels, restaurants, museums, stadiums,
offices, automobile dealerships, auto repair shops, etc. The
geographic data 50 may take a variety of different forms. The
geographic data 50 include data entities corresponding to
"segments" and "nodes." A "segment" is a data entity that
represents a portion of a navigable roadway in the geographic
region and a "node" is a data entity that represents a point in the
geographic region. A "segment" has two "nodes" associated with it,
one at each end.
In one embodiment, the geographic data are developed and provided
by Navigation Technologies Corporation of Rosemont, Ill., however
it is understood that data developed and provided by other entities
may also be suitable for use with the inventive subject matter
disclosed herein.
II. THE NAVIGATION PROGRAMMING
The navigation system 10 may include another storage device 66 (or
ROM) which is used to store navigation programming 68.
Alternatively, the geographic data 50 and the navigation
programming 68 may be provided on a single storage device or
medium. The navigation programming 68 may include separate
applications (or subprograms). These applications provide various
navigation-related features to the user of the navigation system
10. These features may include route calculation, route guidance
(wherein detailed directions are provided for reaching a desired
destination), map display, vehicle positioning (e.g., map
matching), and so on. The navigation applications may be written in
a suitable computer programming language such as C, C++, Java,
Visual Basic, etc.
During a typical use of the navigation system 10 of FIG. 1, some or
all the applications included in the navigation programming 68 are
loaded from the ROM 66 into the memory 28 associated with the
processor 26. The computer 24 receives input from the user
interface 31. The input may include a request for
navigation-related information. Information is obtained from the
positioning system hardware 14 indicating a position of the vehicle
12. The information from the positioning system hardware 14 may be
used by the navigation programming 68 that is run on the processor
26 to determine the location, direction, speed, etc., of the
navigation system 10, and hence the vehicle. The navigation
programming 68 uses the geographic data 50 stored on the storage
medium 52, possibly in conjunction with the outputs from the
positioning system hardware 14, to provide various
navigation-related functions and features. The features provided by
these navigation applications are provided to the user (e.g., the
vehicle driver) by means of the user interface 31.
FIG. 3 is block diagram representing a portion of the navigation
programming 68. The portion of the navigation programming 68 shown
in FIG. 3 includes a route calculation application 75 and a route
guidance application 78. The route calculation application 75
calculates a route from an origin location to a destination
location. The route guidance application 78 provides instructions
to the vehicle driver for following the route calculated by the
route calculation application 75. In FIG. 3, the route calculation
application 75 receives inputs 80. The inputs 80 are derived from
the positioning system hardware 14 and/or user interface 31 (shown
in FIGS. 1 and 2).
The inputs 80 include identifications of an origin and destination.
Using these inputs 80, the route calculation application 75
calculates a route from the origin to the destination. The route
calculation application 75 may use any of various means or
algorithms for this purpose. For example, the route calculation
application 75 may use either the A* algorithm or the Dykstra
algorithm. Methods for calculating routes are disclosed in Ser. No.
08/893,201, filed Mar. 25, 1998, the entire disclosure of which is
incorporated by reference herein. (The methods disclosed in the
aforementioned patent application represent only some of the ways
that routes can be calculated and the subject matter claimed herein
is not limited to any particular method of route calculation. A
suitable route calculation method now known or developed in the
future may be employed.)
Regardless of the method used, the objective of the route
calculation application 75 is to develop a list identifying a
continuous series of road segments that form a legally valid
solution route between the origin and destination. (A "legally
valid solution route" conforms to known traffic restrictions, such
as one way streets, turn restrictions, etc.) The method used by the
route calculation application 75 may be designed to optimize the
solution route to meet one or more predetermined criteria. Such
criteria may include the least travel time, the shortest distance,
the fewest turns, most scenic, etc. If the method used by the route
calculation application 75 is designed to find a solution route
that is optimized for one or more criteria, then the solution route
also ideally meets these one or more criteria. After the route
calculation application 75 has found a solution route, an output 88
is provided to the route guidance application 78.
FIG. 4 is a diagram representing the components of the output 88 of
the route calculation application 75. The route calculation output
88 contains an ordered list 90. Each entry in the ordered list 90
identifies a road segment in the solution route. Each road segment
that forms part of the solution route between the origin and the
destination may be identified by a data entity that represents the
road segment.
Referring again to FIG. 3, using the data in the output 88 of the
route calculation application 75, the route guidance application 78
forms instructions 90 to be provided to the vehicle driver to
follow the calculated route to the destination. The instructions 90
may be provided to the vehicle driver via the user interface 31.
The instructions 90 may be provided as audible instructions using
the speaker 43 of the user interface 31. The instructions may be
provided visually as text, symbols, maps, graphical displays, and
so on, using the display screen 42 of the user interface 31.
III. DETOUR EVALUATION FEATURE
A. First Embodiment
Although navigation systems can provide numerous advantages to
drivers, prior navigation systems have not provided a means to
incorporate an available and potentially very useful source of
navigation-related information, namely driver-observable
conditions. Accordingly, a present embodiment provides a means by
which driver-observable conditions can be incorporated into the
guidance provided by a navigation system.
The driver-observable conditions may include any kinds of
conditions. For example, the driver-observable conditions may
include traffic congestion conditions, scenic conditions, road
surface conditions, road construction conditions, road size
conditions, or any other types of conditions. The driver-observable
conditions may also include whether an upcoming traffic signal
would allow one maneuver (e.g., a left turn) sooner than another
maneuver (e.g., proceeding straight).
In a first embodiment, the navigation system 10 includes a detour
evaluation feature. The detour evaluation feature is provided by
programming in the navigation system 10. Referring to FIG. 3, the
detour evaluation feature may be provided as a separate application
100 in the navigation programming 68. Alternatively, the detour
evaluation feature may be provided as part of another application,
such as the route calculation application 75 or the route guidance
application 78. The detour evaluation feature 100 uses portions of
the route calculation application 75 and the route guidance
application 78. The detour evaluation feature 100 also receives
input from and provides output to the user interface 31.
The detour evaluation feature 100 is described in connection with
FIGS. 5-8. In FIG. 5, the vehicle 12 with the navigation system 10
is shown following a solution route calculated by the navigation
system 10. The vehicle 12 is traveling along a road segment,
labeled "N", which is part the solution route calculated by the
navigation system 10. The solution route calculated by the
navigation system 10 leads to a destination, labeled as such in
FIG. 5. The solution route to the destination includes the segments
labeled N, K, I, G, E, D, and B. (The solution route may also
include other road segments that the vehicle has already
passed.)
In FIG. 5, the vehicle 12 is shown on the road segment labeled "N"
approaching the intersection labeled "INT(1)." As the vehicle
approaches the intersection INT(1), the route guidance feature (78
in FIG. 3) of the navigation system 10 may provide the driver with
instructions to proceed straight through the intersection INT(1) to
the road segment labeled "K", (observing all applicable traffic
laws, of course). According to this embodiment, driver-observable
conditions may be taken into account by the navigation system. For
example, suppose that as the vehicle approaches the intersection,
INT(1), the driver observes that the traffic straight ahead on the
road segment labeled, "K" is congested. The driver may also observe
that the traffic is not as congested on the other segments, labeled
"M" and "L", that lead from the intersection INT(1). When presented
with these observations, the driver desires to be advised by the
navigation system about deviating from the calculated route at the
upcoming intersection. According to one embodiment, the detour
evaluation feature 100 of the navigation system can by used by the
driver to be advised about deviating from the calculated route.
The detour evaluation feature 100 may be operated in several
different modes. In one mode of operation, the detour evaluation
feature operates automatically to evaluate each upcoming
intersection as the vehicle is being driven. In another alternative
mode of operation, the detour evaluation feature is configured to
evaluate only upcoming major intersections, wherein the type of
intersection defined as a major intersection may be configured by
the end user, e.g., only intersections of main business arteries.
In another alternative mode of operation, the detour evaluation
feature can be operated to evaluate only a single selected upcoming
intersection at a time.
FIG. 6 is a flow chart showing the mode of operation of the detour
evaluation feature 100 wherein a single intersection is evaluated.
According to this mode of operation, the driver selects the detour
evaluation feature 100 using the user interface 31 of the
navigation system 10 (Step 110). The driver may select the detour
evaluation feature 100 by operating the input device keypad 36 or
other manual input device of the user interface to select the
detour evaluation feature 100 from an appropriate menu presented on
the display 42 of the user interface 31. Alternatively, the detour
evaluation feature 100 may be activated by the driver using voice
commands if supported by the user interface 31.
When selected by the driver, the detour evaluation feature 100
evaluates deviating from the calculated route at an indicated
location. In one embodiment, the indicated location is the upcoming
intersection by default (Step 114 in FIG. 6). In the example of
FIG. 5, the upcoming intersection is the intersection labeled
"INT(1)." (In alternative embodiments, described below, the
indicated location may be a location other than the upcoming
intersection.)
When evaluating deviations from the calculated route, the detour
evaluation feature 100 first determines which of the possible
deviations from the calculated route at the indicated location are
legally valid (Step 118 in FIG. 6). When performing this step, the
detour evaluation feature 100 checks whether there are any turn
restrictions at the upcoming intersection or whether any of the
roads that meet at the upcoming intersection have a restricted
direction of travel (e.g., are one-way streets) onto which travel
is legally prohibited from the road segment on which the vehicle is
currently located. Any road onto which travel is legally prohibited
is eliminated from consideration as a possible detour from the
calculated route.
The detour evaluation feature 100 evaluates each of the possible
legal deviations from the calculated route at INT(1). Each of these
possible deviations from the calculated route is evaluated relative
to the calculated route 88. The evaluation process performed by the
detour evaluation function 100 is similar to the process used in
the route calculation application 75 when calculating a solution
route. (In one embodiment, the evaluation process may call
functions in the route calculation application 75 to perform the
evaluation.)
When calculating a route, the route calculation application 75 uses
a cost of travel factor associated with each road segment and
intersection. In the geographic database 50, each represented road
segment is associated with a cost of travel factor and/or each
represented intersection is associated with a cost of travel
factor. The cost of travel factor is a value that indicates the
relative cost (e.g., in time) to traverse the segment or
intersection. In FIG. 5, the cost of travel for each depicted road
segment is indicated in the angle brackets next to the road
segment. In general, the higher the cost, the greater the amount of
time to traverse the segment. (For simplicity, the cost of travel
factors for the intersections are not shown. However, each
intersection may have a cost of travel factor associated with each
possible traversal of the intersection.)
The value of the cost of travel factor for a road segment (or an
intersection) may be determined based upon various considerations,
such as the speed limit along the road segment, stop signs or other
traffic restrictions along the road segment, etc. The value of the
cost of travel factor associated with a road segment in the
geographic database is an average value for the road segment and
does not necessarily take into account out of the ordinary
conditions. For example, the value of the cost of travel factor
would not take into account traffic congestion caused by an
accident. The value of the cost of travel factor may not take into
account rush hour traffic conditions.
According to one embodiment, when calculating a solution route, the
route calculation application 75 generally chooses road segments
that have the lowest cost of travel. (In alternative embodiments,
other criteria may be used in addition to or instead of the cost of
travel).
As stated above, when selected by the driver, the detour evaluation
feature 100 evaluates deviations from the calculated route at an
indicated location. When the detour evaluation feature 100 is
selected as the vehicle approaches the intersection labeled INT(1),
the detour evaluation feature evaluates each legal deviation from
the solution route at the upcoming intersection, INT(1). In the
example of FIG. 5, there are two deviations from the calculated
route at the intersection labeled INT(1). The two deviations
include turning right onto the segment labeled "M" and turning left
onto the segment labeled "L". In order to evaluate these two
deviations, the detour evaluation feature 100 first determines the
sums of the costs of travel associated with each of these
deviations (Step 120 in FIG. 6). For the deviation onto "L", the
total cost of travel includes the individual costs associated with
the segments labeled L, J, G, E, D, and B. These individual costs
are 18, 7, 10, 10, 5, and 15, respectively, which sum to 65. For
the deviation onto the segment labeled "M", the cost of travel
includes the individual costs associated with the segments labeled
M, Q, R, and A. These individual costs are 9, 65, 50, and 10,
respectively, which sum to 134. The total cost of travel associated
with staying on the solution route is also obtained. As stated
above, the remaining segments in the solution route include the
segments labeled K, I, G, E, D, and B. The individual costs of
these segments are 12, 12, 10, 10, 5, and 15, respectively, which
sum to 64.
Once these total costs of travel are determined, the total cost of
travel of each deviation from the solution route is compared to the
total cost of travel of the remaining segments in the solution
route (Step 124 in FIG. 6). In the example of FIG. 5, the total
cost of travel of the deviation of turning right, i.e., 134, is
compared to the total cost of travel of remaining on the solution
route, i.e., 64. Likewise, the total cost of travel of the
deviation of turning left, i.e., 65, is compared to the total cost
of travel of remaining on the solution route, i.e., 64. Using these
comparisons, the detour evaluation function 100 provides one or
more evaluations to the driver.
Different kinds of evaluations can be provided by the detour
evaluation feature 100. In one embodiment, the evaluation provided
by the detour evaluation feature 100 is an indication not to make a
deviation at an indicated location. When the detour evaluation
feature 100 provides an indication not to make a deviation, a
threshold factor 128 may be used with the comparisons made between
the deviations and the solution route. For example, a threshold
factor of 25% may be used. Using a threshold factor of 25%, if the
deviation has a cost of travel that is greater than 125% of the
cost of travel of the solution route, the detour evaluation feature
100 provides an indication to the driver not to make the deviation.
In the example of FIG. 5, making a right turn has a cost of travel
of 134 compared to a cost of travel of the solution route of 64.
The cost of travel of the right turn deviation is 209% of the cost
of travel of the solution route (134/64=209%). Therefore, since
this value exceeds 125%, the detour evaluation feature 100 provides
an indication to the driver not to take the deviation.
On the other hand, making a left turn has a cost of travel of 65
compared to a cost of travel of the solution route of 64. The cost
of travel of the left turn deviation is 106% of the cost of travel
of the solution route (65/64=106%). Therefore, since this value is
less than 125%, the detour evaluation feature 100 does not indicate
to the driver to avoid the left turn deviation.
In one embodiment, the threshold factor 128 is configurable by the
end user. A setup program included in the programming 68 may be
used for this purpose. The end user may be able to access a menu on
the display from which a value for the threshold may be selected.
For example, the threshold factor may be set by the end user at
10%, 50%, 100%, and so on.
After applying the threshold factor to the comparisons of the
deviations to the solution route, the detour evaluation feature 100
provides an evaluation result to the end user (Step 130 in FIG. 6).
In one embodiment the evaluation result is an indication. The
indication can be expressed as text (e.g., "DON'T TURN RIGHT AT THE
UPCOMING INTERSECTION") or a graphical display on the display
screen 42 (in FIG. 1) or an audio message conveyed over the speaker
43 (in FIG. 1). One example of a graphical display showing an
indication 144 not to make a right turn at an intersection being
approached is shown in FIG. 7.
Referring again to FIG. 5, the driver may choose to stay on the
solution route. If he/she does, the vehicle is driven onto the
segment labeled "K." The detour evaluation feature 100 may be
operated again as the vehicle approaches the next location at which
a deviation from the solution route can be made. This next location
is the intersection labeled, "INT(2)." At the intersection labeled
INT(2), the solution route calls for making a right turn onto the
segment labeled "G." The detour evaluation feature 100 would have
only one deviation to evaluate at INT(2), i.e., proceeding straight
onto the segment labeled "H." Assuming that travel onto "H" from
"I" is legal, the detour evaluation feature 100 determines the cost
of detouring onto "H" versus the cost of staying on the solution
route by turning right onto "G." In this case, the deviation onto
"H" has a total cost of 42 and the remaining portion of the
solution route has a total cost of 40. Using the threshold factor
of 25%, the detour evaluation feature 100 provides an indication to
the end user that deviating from the solution route by proceeding
onto "H" is not substantially worse than following the solution
route onto "G."
B. Evaluating Other Locations Along Solution Route.
As mentioned above, in one embodiment the indicated location at
which the detour evaluation feature 100 evaluates a deviation from
the calculated route is by default the immediate location ahead
along the solution route at which a departure from the solution
route can be made. In many cases, this location will be an upcoming
intersection. In alternative embodiments, the driver may select a
different location from which deviations are evaluated.
To allow the end user to select a different location at which to
evaluate a deviation from the solution route, the detour evaluation
feature 100 presents menu screens from which the end user can
select a location other than the upcoming intersection. In one
embodiment, the detour evaluation feature 100 presents each
location at which a deviation from the solution route can be made
starting with the intersection immediately ahead of the vehicle on
the solution route and proceeding one at a time to each subsequent
location along the solution route at which a deviation from the
solution route can be made (Step 130 in FIG. 6). Each location may
be presented to the user in a graphical form. The display screen
would include an indication of a key to press on the user interface
to have an evaluation made of the deviations from the solution
route at the displayed intersection. The display screen would also
include an indication of another key to press to scroll to another
display screen that illustrates the next location along the
solution route at which a deviation from the solution route can be
made. The detour evaluation feature 100 includes a step (Step 134
in FIG. 6) that accepts the user's input and either performs the
evaluation of the deviations from the solution route at the
displayed location or displays the next location along the solution
route at which a deviation can be made. Using the above process,
the end user may obtain evaluations for deviations from the
solution route at more than one location.
In another alternative, the detour evaluation feature 100 evaluates
all the locations within a driver-observable distance along the
solution route from which a deviation from the solution route can
be made. ("Driver observable" may just what the driver sees down
the road through the windshield, or alternatively "driver
observable" may mean what the driver observes in terms of radio
traffic reports, or programmable message boards on the highway, or
road construction.)
C. Replacement of Old Solution Route with New Solution Route
After the end user is presented with an evaluation of deviations
from the solution route by the detour evaluation feature 100, the
end user may choose to follow one of the deviations instead of
continuing on the solution route. If the end user proceeds along a
deviation, the navigation programming uses the deviation as a new
solution route. The route guidance application 78 would provide the
end user with instructions to follow the new solution route to the
destination. Thereafter, when the vehicle approaches an
intersection and the detour evaluation feature 100 is selected,
deviations are determined from the new solution route. If the new
solution route crosses the original solution route, a deviation
from a new solution route may include resuming travel along the
original solution route.
D. Alternative Presentation of Evaluation Results
In the embodiment described above, the evaluation result provided
to the end user by the detour evaluation feature 100 included an
indication whether to avoid a deviation at an upcoming location
along the solution route. In alternative embodiment, the detour
evaluation feature 100 may present different kinds of evaluation
results to the end user. One alternative type of evaluation result
is shown in FIG. 8. FIG. 8 shows an illustration of the same
intersection, INT(1) shown in FIG. 7. In FIG. 8, instead of showing
an indication not to make a right turn, the detour evaluation
feature 100 provides numeric indications 150 associated with each
of the possible legal deviations and the solution route. The
numeric indications 150 may provide the expected travel times
associated with each of the possible legal deviations and the
solution route. The expected travel times may be derived from a
relationship that estimates the time of travel from the total cost
of travel for each of the possible legal deviations and the
solution route. These numeric indications 150 are intended to be
only estimates, but they may provide the end user with information
about the relative times of travel of each alternative from which a
decision can be made whether to follow the solution route or take
one of the deviations.
In another alternative embodiment, the numeric indications 150 may
indicate the expected times of arrival at the destination.
In another alternative embodiment, the numeric indications 150 may
indicate how much longer each deviation is expected to take
compared to the solution route.
In another alternative embodiment, the numeric indications 150 may
indicate the remaining traveling distance to the destination
associated with each of the alternative paths leading from the
upcoming intersection. Alternatively, the numeric indications 150
may indicate the incremental traveling distance to the destination
associated with each of the alternatives paths.
E. Alternative Modes of Operation
(1). U-turns
In the aforementioned embodiments, detours from the solution route
were evaluated at locations at which a departure from the solution
route can be made. In an alternative mode of operation, the detour
evaluation feature can also take into account U-turns from the
present location of the vehicle. Thus, according to this
alternative mode of operation, if the detour evaluation feature is
selected when a vehicle is approaching an intersection, the
deviations that are evaluated would include making a U-tum
(provided that a U-tum was possible and/or legal at the current
vehicle location), as well as any maneuvers at the intersection.
The cost of the U-turn deviation would be determined in the same
manner as the costs of the other deviations. Likewise, the detour
evaluation feature would provide an evaluation result to the end
user about the U-turn deviation in the same way as evaluation
results are provided about the other deviations.
Whether the detour evaluation feature 100 evaluates U-turns may be
configured by the end user. A menu screen in a setup program may be
provided for this purpose.
The U-turn deviation may be used when the vehicle is along a
solution route leading up to a railroad grade crossing. When a
vehicle is stopped at a railroad grade crossing, the vehicle driver
may use the detour evaluation feature, including U-turns, to
determine whether to make a U-turn or wait for the train to
pass.
(2). Interactive Mode
According to another embodiment, the detour evaluation feature of
the navigation system can be operated in an interactive mode.
According to this embodiment, the end user does not have the
navigation system calculate a single solution route to destination
beforehand. Instead, the end user indicates a destination to the
navigation system. Then, the driver begins to drive toward the
destination. As each intersection is approached (including entrance
and exit ramps), the navigation system provides an evaluation of
all the legal maneuvers (e.g., including all turns and remaining
straight on the road). The evaluation process may be made using the
cost of travel associated with each alternative path to the
destination from the upcoming intersection being evaluated, as
described above. The evaluation result provided to the end user may
take any of the forms described above. For example, the navigation
system may provide an indication not to make a turn, as illustrated
in FIG. 7. Alternatively, the navigation system may provide
separate indications of the relative costs of each turn at an
upcoming intersection.
When operated in this manner, the driver uses the information
provided by the navigation system interactively. The driver may
choose to follow any one of the roads leading from the intersection
based upon (1) the evaluations provided by the navigation system
and (2) his/her own observations of conditions or driving
preferences. As mentioned above, the conditions observed may
include any kinds of conditions, such as traffic congestion,
traffic light status, road conditions, scenic conditions, and so
on.
(3). Background Operation
The evaluation functions of the detour evaluation feature 100 may
be operated in the background while the vehicle is being driven
along the solution route. In this way, when the user selects the
detour evaluation feature 100, the evaluation results may be
provided to the user very quickly. Whether detour evaluation
feature operates in the background may be configured by the end
user.
(4). Alternative Modes of Operation
As stated above, the detour evaluation feature may be operated in
different modes of operation, including a mode in which each
upcoming intersection is evaluated automatically as the vehicle is
being driven. In another alternative mode of operation, the detour
evaluation feature is configured so that only certain types of
upcoming intersections are evaluated automatically. Using a setup
menu, the user may select the types of intersections for which the
detour evaluation feature operates automatically. For example, the
user may configure the detour evaluation feature so that only major
intersections or intersections of business roads are evaluated
automatically. In another example, the detour evaluation feature
may be configured so that it automatically evaluates only
intersections with stoplights. In another example, the detour
evaluation feature may be configured so that it automatically
evaluates only intersections with roads of a selected rank or
higher, wherein a rank of a road is related to its functional
classification.
In a farther example, the detour evaluation feature may be
configured to take into account the kind of road on which the
vehicle is presently travelling when automatically evaluating
upcoming intersections. For example, if the vehicle is on a low
ranked road, e.g., a side street, the detour evaluation feature
automatically evaluates each upcoming intersection. However, if the
vehicle is on a higher ranked road, e.g., a major road artery, only
intersections with stoplights are automatically evaluated.
In yet another example, the detour evaluation feature may be
configured to take into account the vehicle speed when
automatically evaluating upcoming intersections. For example, if
the vehicle is traveling below the speed limit, the detour
evaluation feature automatically evaluates each upcoming
intersection. However, if the vehicle is traveling at or close to
the speed limit, only intersections with stoplights are
automatically evaluated.
(5). Suppression of Minor Deviation Routes
According to another alternative, when the detour evaluation
feature is used to evaluate deviations from a calculated solution
route at an indicated location, the deviations may be required to
avoid some or all the road segments in the calculated solution
route for some or all the remaining distance from the indicated
location to the destination. By avoiding road segments in the
calculated solution route, the deviation routes are more likely to
be substantially different from the solution route. This avoids
consideration of deviation routes that represent only minor
departures from the solution route, e.g., departures that leave the
calculated solution route at the upcoming intersection and then
immediately rejoin the solution route at the next intersection.
This feature may be configurable by the end user.
(6). User-selection of Route Suppression
According to another alternative, when the detour evaluation
feature is used to evaluate deviations from a calculated solution
route at an indicated location, the deviations may be required to
avoid specific road segments identified by the end user. According
to this embodiment, the end user is given a means to identify road
segments to avoid. For example, these road segments may include
portions of the original solution route. Then, when the deviation
evaluation feature is used to evaluate deviations from the solution
route, these identified roads segments are not included in any
possible deviation routes.
It is intended that the foregoing detailed description be regarded
as illustrative rather than limiting and that it is understood that
the following claims including all equivalents are intended to
define the scope of the invention.
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